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close this bookCentral Eurasian Water Crisis: Caspian, Aral, and Dead Seas (UNU, 1998, 203 pages)
close this folderPart III: The Caspian Sea
close this folder8. Environmental policy-making for sustainable development of the Caspian Sea area
View the document(introduction...)
View the documentIntroduction
View the documentMorphometry and the principal hydrological features
View the documentThe water balance and water-level variations
View the documentThe economic impacts on the Caspian states of the water-level variations
View the documentOther development issues requiring international cooperation
View the documentConclusions
View the documentAcknowledgement
View the documentReferences

The water balance and water-level variations

The data on the Sea's water balance vary considerably, depending on the time-period being considered and the incompleteness of knowledge. It is not the objective of this paper to go deeply into these issues. As an illustration, however, average data for 1900-1985 are shown in table 8.1. The mean annual deficit of the water balance 12 km3 - corresponds to the mean annual drop in water level of 3.1 cm. The average water level for the 1900-1985 period was - 27.35 m above sealevel (a.s.l.), or 27.35 m below the ocean level.

Most components of the water balance do not need explanation.

Table 8.1 The average water balance of the Caspian Sea, 1900-1985

Component

km3/year

River inflow

+298

Precipitation on the Sea's surface

+74

Evaporation from the Sea's surface

-370

Outflow to the Bay of Kara-Bogaz-Gol

-14

Total

-12

Source: adjusted data from Kosarev and Makarova (1988).

The Kara-Bogaz-Gol is a large bay situated on the eastern side of the Caspian Sea. Because of its elevation, there is a constant flow in one direction, from the Sea to the bay, with subsequent evaporation of water from the bay.

The variations in the components of the Caspian water balance are considerable; this leads to large changes in water level. The main factor in variations in the water balance is changes in river runoff, particularly that of the Volga.

During the twentieth century, the main periods of change in the Caspian Sea's water regime were as follows (Kuksa, 1994):

1900-1929:

Relative stability of the water balance. The water level oscillated slightly around 26.2 m below sea level.

1930-1941:

A very large deficit in the water balance of 62 km3, mainly because of the decrease in river runoff (mostly that of the Volga). The water deficit led to a sharp drop in the water level of 1.8 m.

1942-1977:

A modest deficit in the water balance mainly because of a decrease in river runoff. During this period there was a drop in the water level of an additional 1.3 m.

1978-present:

A positive water balance. The water level has been increasing from its lowest point of -29.0 m in 1977. By 1994 it had risen to about -26.5 m, an increase in this period of 2.5 m.

For not very clear seasons, researchers in the 1970s and earlier were under the impression that water withdrawals in the Caspian basin, mainly for irrigation and to fill the large, newly constructed water reservoirs, played a decisive role in variations in the water balance. In fact, variations of natural origin explain about 90 per cent of all variations (Golytsyn and Panin, 1989). Water withdrawals in the Sea basin amount to 40-50 km3/year, about half of which are from the Volga basin. Without human interference, the Sea's level might have been about 1.5 m higher than it is now (Kuksa, 1994).

The continuous, prolonged drop in the level of the Caspian caused a panic that reached its height in the 1970s. A number of long-term water-level projections were published, using different approaches to forecasting. Some were based on analysis of inflow to and evaporation from the Sea. They were not successful, because the behaviour of these factors is close to that of "white noise." Attempts were made to base projections on the index of solar radiation (the so-called Wolf's numbers), but they proved to be very contradictory. Forecasts based on indices of atmospheric circulation also provided unstable results. The only seemingly reasonable basis for projections was the forecast of water withdrawals, and this approach led to the conclusion that the level of the Caspian Sea would continue to fall (Shiklomanov, 1979). The common opinion that the level of the Caspian Sea would continue to drop had been strongly reinforced by the similar sharp drop in the level of the Aral Sea just a few hundred kilometres to the east of the Caspian Sea.

Very drastic and very costly measures were considered to maintain the level of the Caspian. Projects were proposed to bring large amounts of water from the north (e.g. Siberian rivers) to the south of the country (Golubev and Biswas, 1979, 1985). If they had been carried out, they would have had unforeseen and costly consequences.

In the 1980s, the situation changed completely. The Caspian water level continued to rise. Since all kinds of forecasts had indicated the continuation of a declining sealevel, this can serve as an example of a collective miscalculation by many very good water experts. The sealevel, however, has continued to grow in the 1990s, generating worries for the future, although actual problems of inundation and destruction as well as recent sealevel rises have had a major effect on the economy of locales around the Sea's shore.

The situation of oscillations in the level of the Caspian Sea is typical of closed lakes. It is typical not only from the hydrometeorological point of view, but from the point of view of economic impacts as well. The variations in sealevel cause uncertainty over time in economic activities. The interest groups involved, including governments, have to develop a long-term strategy for the management of the region. Thus, it is important to determine the expected upper and lower extremes with a reasonable probability of occurrence.

The history of variations in the level of the Caspian Sea (Klige, 1992) provides useful insights into this issue. During the period of instrumental observations (fig. 8.1) from 1837 on, the water level varied between -25 m and -29 m a.s.l., with an average of -27 m. From the sixth century B.C. to the present, the sealevel ranged from -20 m to - 34 m, a variation of 14 m (fig. 8.2). The average level, however, was the same: -27 m. During the Holocene (the past 10,000-11,000 years), the sealevel ranged from - 9 m to - 34 m (fig. 8.3), a variation of 25 m. The mean sealevel was -25 m a.s.l. (Note that the curves in these figures are not completely consistent, owing to differences of methodology and measurement.)


Fig. 8.1 Variations in the water level of the Caspian Sea according to instrumental observations, 1837-2000 (Source: Klige, 1992)

The rates of water-level change are also important. The typical rate for pronounced changes is about 150 cm per 10 years; this happened twice in the twentieth century. Over longer periods of time, the typical figure for sharp changes is about 10 m over a period of 1,000 years. If one is to believe the data in figure 8.3, the extreme rate of change is about 14 m over 300 years; or a 14 m increase and then a 14 m drop over 700-800 years. Thus, sharp variations in the level of the Caspian Sea are the most characteristic feature of its regime at time-scales of tens and hundreds of years. Economic development strategies must take this into consideration.

The unsuccessful experiences with forecasting Caspian Sea behaviour indicate that, given the present-day level of scientific understanding, reliable forecasts cannot be expected. One has to plan on the basis of expectations of quasi-cyclical oscillations in sealevel, as has happened in the past. Most researchers believe that in the next decade the sealevel will reach -25 m. In the longer term, variations in sealevel are expected to range between -20 m and -29 m.


Fig. 8.2 Variations in the water level of the Caspian Sea during historic time (sixth century B.C. to the present) (Source: Klige, 1992)


Fig. 8.3 Variations in the water level of the Caspian Sea during the Holocene (Source: Klige, 1992)

During the prolonged drop in sealevel between 1930 and 1977, when it was believed that the trend would continue, economic planning considered the low sealevel. New settlements or roads, ports, oil installations, and so forth were built on the assumption of a sealevel of -28 m. Now, however, with the sealevel approaching -26 m, economic damage in each of the riparian countries has been enormous.

Owing to the relatively rapid rise in sealevel, the Caspian coastline is currently in a state of transition. In general, the change from the retreating phase of the Caspian to the advancing phase has led to a transition from predominantly accumulating processes along the shore to a prevalence of abrasion processes. On formerly accumulating shores, erosion processes have begun and continue in many places. In quite a number of areas erosion has been catastrophic. Cliffs used to be separated from the Sea by a wide beach. Now, the cliffs are subjected to wave action, and the eroded soils have accumulated on the former beaches. Many houses, apartment buildings, hotels, and other structures constructed in the 1930s to 1970s close to the cliffs are now in danger or are in the process of being destroyed. Experience has shown that construction of any kind, except ports, should be at levels above -23 m.